diff --git a/tangostationcontrol/tangostationcontrol/beam/delays.py b/tangostationcontrol/tangostationcontrol/beam/delays.py
index c080da244b05ac42e7e95a0eebfcf2966a6a213d..da649342de07200e96645d7ad4c3011eae416720 100644
--- a/tangostationcontrol/tangostationcontrol/beam/delays.py
+++ b/tangostationcontrol/tangostationcontrol/beam/delays.py
@@ -2,7 +2,7 @@ import casacore.measures
 import numpy
 import datetime
 
-def subtract(a, b):
+def subtract(a, b) -> numpy.ndarray:
     return numpy.array([x - y for x, y in zip(a, b)])
 
 
@@ -54,7 +54,8 @@ class Delays:
         # Return array [directions][angles]
         return direction_vectors.T
 
-    def is_valid_direction(self, direction):
+    def is_valid_direction(self, direction) -> bool:
+        """ Check validity of the direction measure """
         try:
             _ = self.measure.direction(*direction)
         except (RuntimeError, TypeError) as e:
@@ -62,7 +63,7 @@ class Delays:
 
         return True
 
-    def delays(self, direction, antenna_absolute_itrf: list([float])):
+    def delays(self, direction, antenna_absolute_itrf: list([float])) -> numpy.ndarray:
         """ Get the delays for a direction and *absolute* antenna positions.
         
             Returns delays[antenna]. """